Conventionally, there are apparatuses that detect magnetic characteristic information of sheets that are being conveyed, using a magnetic sensor, thereby inspecting the authenticity, the type, and the like of the sheets. In such apparatuses, in the case of using a magnetic sensor including a plurality of magnetic sensing portions arranged in a direction orthogonal to the sheet conveying direction in order to perform precise detection throughout the entire area of a sheet, it is necessary to correct unevenness in sensitivity of the plurality of magnetic sensing portions. When correcting the unevenness in sensitivity, there is a demand for shortening the time required to adjust the sensitivity, by simultaneously adjusting the sensitivity of all of the plurality of magnetic sensing portions. Furthermore, there is a demand for improving the level of precision in adjusting the sensitivity, by stably generating a magnetic field that precisely resembles a change in magnetic field lines in the case where a sheet is actually detected.